a) Field of the Invention
This invention relates to an impeller pump for use with hot-water serving systems to supply hot water.
b) Description of the prior art
An impeller pump is used to supply hot water from the hot water serving system, such as a jar and pot. As shown in FIG. 1, the impeller pump has a suction port connected through a connecting member 34 with a bottom opening of a hot water container 20. In FIG. 1, the impeller pump comprises a pump casing 21, a partition plate 22 for gas-tightly separating a pump chamber 23 from a driving device 24, and a shaft 25 supported by a supporting member 26. A retaining member 27 is used to keep an impeller 28, which is rotatably placed on the shaft 25, and a driven magnet 29, respectively. A driving magnet 30 is rotated by an electric motor 31.
In the impeller pump of FIG. 1, the driving magnet 30 is rotated by the electric motor 31. The driven magnet 29 is then rotated by the magnetic coupling action between the driving magnet 30 and the driven magnet 29, thereby causing the impeller 28 to rotate. Thus, due to the rotation of the impeller, hot water in the container 20 is sucked into the pump chamber 23 through the inlet port 32, and then discharged out of the pump through a discharge port 33 for the intended supply.
When hot water is being supplied by using such an impeller pump, there is a problem that bubbles are generated in the pump chamber. Particularly, the pressure in a region around the impeller's axis of rotation becomes lower than elsewhere. Thus, bubbles generated tend to gather around the axis of rotation and choke off the suction port, thereby obstructing the flow of hot water, substantially lowering the hot water supply capacity and often stopping the hot water supply.